Method of and device for continuously crystallizing iron sulfate hepta-hy-drate fromsulfates of mordanting solutions



y 6, 1965 P. NIEDNER 3,193,361

METHOD OF AND DEVICE FOR CONTINUOUSLY CRYSTALLIZING IRON SULFATE HEPTA-HYDRATE FROM SULFATES OF MORDANTING SOLUTIONS Filed April 7, 1961 3 Sheets-Sheet 1 T-lllllunmy 5, 1955 P. NIEDNER 3,193,361

' METHOD OF AND DEVICE FOR CONTINUOUSLY CRYSTALLIZING IRON SULFATE HEP'1'A--I'IYDRAI"E FROM SULFATES OF MORDANTING SOLUTIONS Filed April 7. 1961 s Sheets-Sheet 2 f r2 rs 1P I I I I E 26 i P. NIEDNER 3,193,361 CON ON SULFATE ULFATES OF MORDANTING SOLUTIQNS July 6, 1965 METHOD OF AND DEVICE FOR TINUOUSLY CRYSTALLIZING IR HEPTA-HYDRATE FROM S Filed April 7, 1961 3 Sheets-Sheet 5 United States Patent Oilice 3,l%,36l Patented July 6, 1965 Filed Apr. 7, E61, Se No. 101,478 Claims priority, application Germany, Apr. 13, 196%,

s Gaims. in. 23-405 The present invention relates to a method of and device for continuously crystallizing iron sulfate-heptahydrate from sulfates of mordanting solutions by means of a cooling operation.

Methods are known according to which the mordanting solutions are cooled in containers by means of liquid cooled surfaces, and in which the formed crystals collect in the lower, in most instances, conical portion of the containers. With this method, relatively long crystallization periods can be obtained so that they are particularly suitable for the formation and separation of large crystals. The mordanting solution is in this connection usually agitated by means of agitators. This method, however, has the drawback that a continuous withdrawal of the crystalline paste at the bottom of the containers can be carried out by bottom valves only under great circumstances so that this method does not permit a continuous processing or preparation.

There are also known various methods according to which the mordanting solutions are cooled by an air flow which is passed in counter-current to the mordanting solutions. With this type of cooling of the mordanting solutions, a cooling down to approximately 30 Centigrade only can be obtained. Since, on the other hand, a preparation of mordanting solutions by cooling down to 30 centigrade is unsatisfactory for the mordanting operation, in view of too high a constant in salt of the mordanting bath, air cooled crystallization devices have been supplemented by liquid cooling systems of the type described above which follow said air cooling systems. However, inasmuch as air cooled crystallizing devices work in a continuous manner, whereas the water cooled crystallizing devices following said air cooled crystallizing devices do not work in a continuous manner, such combined air and liquid cooled crystallizing devices have not been adopted in practice over vacuum crystallizing devices which operate in a completely continuous manner.

It is, therefore, an object of the present invention to provide an air cooled and liquid cooled crystallizing method and device for carrying out such method which will allow a completely continuous operation for the purpose set forth above.

It is also an object of this invention to provide a method of and device for crystallizing iron sulfate heptahydrate from sulfates of mordanting solutions while employing an air-liquid cooled system, which will have a low energy consumption and which will be free from mechanical parts exposed to wear and corrosion.

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings, in which:

FIG. 1 represents a diagrammatic total view of a crystallizing container according to the invention with two treatment chambers.

FIG. 2 is a diagrammatic showing of two serially arranged crystallizing containers of the type shown in FIG. 1.

FIG. 3 is a particularly advantageous construction according to the invention of a combined number of feeding and agitating devices.

In contrast to heretofore known methods, according to the present invention, the cooling of the mordanting solutions is effected by air and water together in one method step. More specifically, according to one embodiment of the method according to the invention of continuously crystallizing iron sulfate hepta-hydrate from sulfates of mordanting solutions, in which the said solutions are introduced into one or more containers, are then cooled in said containers by an air stream and by means of liquid cooled surfaces, and in which the formed crystals collect at the lower conical portion of the container, the invention consists in that the liquid to be treated is passed through at least two inter-communicating treatment chambers and is continuously agitated in said containers in such a way that the liquid flows in one treatment chamber downwardly and in the other treatment chamber upwardly. Furthermore, the liquid is by means of cooling coils cooled in one or in both chambers. Compressed pre-cooled air for advancing and cooling the liquid is introduced into the lower portion of one of the two chambers, and the crystals being deposited in the lower portion of the container are by means of pneumatic feeding means moved upwardly and are withdrawn above the container.

With this method there is obtained the particularly favorable effect that the air blown into the treatment chamber simultaneously serves for cooling and agitating the container content for purposes of overcoming the meta stable dissoluble range for distributing crystal seeds and thereby growing crystals of desired size. Inasmuch as the air passing through the container absorbs only a portion of the quantity of heat to be conducted away, the further cooling and thereby the conducting away of the remaining heat is etfected by the cooling coils arranged in the container. The heat transferred to the cooling coils is intensified in an advantageous manner by the agitation of the mordanting liquid, which agitation is effected by the air flow.

According to a further embodiment of the invention, the liquid to be treated is introduced into a container with circular cross section and conical lower portion. The liquid moves downwardly in said conical lower portion outside a cylindrical pipe which is coaxially arranged within the interior of the container and separates the two treatment chambers from each other. After the liquid has sunk down into the range of the conical lower portion of the container it will rise again from there through a treatment chamber within the cylindrical pipe. For pur poses of obtaining a fast rising movement, air is at the lower end of the inner treatment chamber blown into the latter by means of a nozzle ring. A very important feature of the invention is seen in the fact that the liquid to be treated passes through the treatment chambers at relatively high speed whereby a deposit of crystals on the walls, pipes, cooling coils etc. will be prevented. The above described method may also be carried out in such a way that first the treating liquid is introduced into the treatment chamber located within the cylindrical pipe, and that after the treating liquid has passed this chamber, it will again rise in the outer treatment chamber having an annular cross section, while air is blown into said chamber through a nozzle ring arranged at the lower end of the outer treatment chamber.

According to a further feature of the present invention, the upwardly and downwardly directed flow of the liquid is in both treatment chambers adjusted by controlling the supply of air in such a way that fine crystals will be held in suspension, whereas larger crystals will have the possibility of depositing themselves. By means of trol of the throughput quantity is effected by a distributing device at the exit of the conveying device. To this end, the required throughput is branched off from the distr-ibuting device, and the remainder is returned into the container.

A further embodiment in the method according to the 7 pneumatic feeding device or nozzle ring. For purposes of obtaining a counter-current cooling effect, a plurality of identical crystallizing steps may be arranged in series with regard to each other.

A device for carrying out the method according to the ,present invention comprises primarily a cylindrical crystallizing container of a considerable height with regard to its diameter and with a conical bottom section, and a cylindrical pipe arranged in the interior of said container and coaxial ly therewith. The said cylindrical pipe ends a withdrawal pipe 22. The air blown into the tank is Withdrawn through pipe 22. The upper end of tank 2. is furthermore provided with .an overflow pipe 20.

Within the interior of the tank 2 there is provided a cylindrical pipe 9 which is coaXially arranged with regard to the wall of tank 2 and which separates the two treatment chamber from each other. The cylindrical pipe 9 may simultaneously be designed as cooling body, for instance in the manner of a cylindrical cooling pocket. The withdrawal of the mordanting liquid from the lower conical portion 2a of the tank is effected through a pipe 13 which extends through the entire length of the tank and is arranged in the central portion thereof. Pipe 13 extends through lid 21 and leads into a head container 11. The ends of the pipe 13 are somewhat widened in the manner of a trumpet in order to displace the growing of crystals into a range in which the pipe cross s ction is not impeded directly by the growing crystals. The

at a certain distance below the upper container lid and sub-divides the container in two treatment chambers. In the interior and/ or outer treatment chamber, there are provided cooling coils. The arrangement furthermore comprises a nozzle ring at the lower end of the outer or inner treatment chamber and a feeder pipe in the center of the container. The said feeder pipe starts within the range of the conical container portion and ends above the container in a separate head container.

With the above mentioned advantageous embodiment of the device, the cylindrical pipe in the interior of the container may simultaneously be designed as cooling body, for instance in form of an annular cooling pocket. It is also a characterizing feature of'the invention that at least above the lower end of the feeder pipe there is provided a nozzle ring surrounding said feeder pipe for blowing in air. Furthermore, the two ends of said feeder pipe are provided with trumpet-like enlargements. The upper end of the feeder pipe extends into its head container which consists of a transparent synthetic material as for instance transparent polyvinyl chloride, and has a bottom which is inclined toward the discharge pipe. Mounted in said head container are an impact and devia-ting body which are arranged transverse to the flow direction above the outlet opening of the feeder pipe. The head container has furthermore mounted thereon a discharge pipe through which the acid containing air is withdrawn. The distributing device mounted on the discharge pipe of the head container comprises a forked member which i rotatable relative to the discharge pipe. According to a further feature of the invention, the

feeder pipe, the nozzle crown, the nozzle ring, the

supply lines to the same, the head container, a base plate supporting the head container, and the connections for connecting the air lines are combined to an exchangeable unit which is characterized by smooth air stream lined outer con-tours so as not to afford any port tions where the crystals might be deposited.

Referring now to the drawings in detail and FIG. 1 thereof in particular, the arrangement shown therein represents a crystallization container with a tank 2, into which the mordanting liquid (Beizfliissigkeit) to be regenerated is introduced into the pipe line 1. The lower 'end 2a of tank 2 is conical and is provided with a connection 2b having interposed therein an outlet valve 3 through which the treatment liquid may be discharged when it is intended to clean the tank. The upper end ofthe tank is closed by a lid 21 having connected thereto pipe 13 which may be termed conveyor pipe is advantageously formed-as a seamless pipe of synthetic material as for instance polyvinyl chloride.

The introduction of air into conveyor pipe 13 is effected through a nozze crown 14 which surrounds the feeder pipe near the lower end thereof. That portion of conveyor pipe 13 which is surrounded by the nozzle crown 14 is provided with apertures for the entrance of air into the interior of pipe 13. The nozzle crown 14 receives its air through the conduit system 6, valve 16, and through a conduit 16a extending through the tank. The lower end of cylindrical pipe 9 has concentrically arranged thereto a nozzle ring 5 through which compressed air is blown into the interior of the treatment chamber, said air being introduced from the outside through conduit system 6, valve 7 and corresponding conduit means 7a.

The cooling of the treatment liquid through liquid cooled surfaces is with the arrangement shown in the drawing effected by means of cooling coi ls 10 with an inlet tube 10a and an outlet tube 10b for the cooling liquid which are co axially arranged with regard to tank 2 and extend approximately over its entire height on one hand in the outer treatment chamber and on the other hand in the inner treatment chamber. However, it is also possible to arrange the cooling coil in one (if the two treatment chambers only. This will depend from the required cooling output. The conduits through which air is conveyed to the conveyor pipe 13 and nozzle ring 5 have furthermore connected thereto scavenging connections 8 through which scavenging air is passed if the pipe lines should clog up. The head container at the upper end of the conveyor pipe 13 is equipped with a bottom 19 which is inclined in' conformity with the incline tion of the discharge pipe 15. This inclination is at an angle of 45 in the drawing in order to allow an easy discharge of the crystals through the discharge pipe. Connected to the lid of the container 11 is a pipe 13 through which the acid containing air is withdrawn flom the container 1 1. In order to be able easily to observe the feeding operation, the container 1 1 is advantageously made of a transparent synthetic material.

The crystallizing device of FIG. 1 operates in the following manner. The mordanting liquid introduced into the apparatus through pipe line 1 first sinks down in the outer treatment chamber into the lower conical portion 2a of tank 2. Here it is agitated and subjected to a relatlvely fast upward movement through the inner treatment chamber by the air blown into the conical part 2a by means of the nozzle ring 5. In this way, a continuous in a transverse direction thereto. In this way, due to the high velocities at which the circulatory flow hits and passes said coils, favorable heat transfer values will be obtained, and the cooling coils will, due to the strong eddy current formation, always be washed clean of any possibly adhering crystal crusts.

The formed crystals are collected the conical portion 2a of tank 2 and from here are by means of the pneumatic conveying device 12 first moved into the head container 11 and finally are passed through a pipe line and distributing device into the respective adjacent container or centrifuge and/or crystallizing tank 2 (not shown). In view of the air blown into the conical portion 2a through the nozzle ring 14, an air-mordanting liquid-crystal paste mixture will rise in pipe 13 at high velocity and will impinge upon the impact and deviating body 17. Due to the impact and the deviation of the mixture, the air will be separated from the mordanting liquid and the crystal paste and will be withdrawn through the pipe system 18. After having left the deviating body 17, the niordanting liquid and the crystal paste will at a downwardly inclined angle be thrown against the wall of the container 11 from where the remaining mixture will flow along the inclined bottom and will be discharged through the pipe and distributing system 15.

The control of the pneumatic conveying device 12 is, in conformity with the present invention, effected by the distributing device 15. The pneumatic conveying device 12 conveys a multiple of the quantity to be discharged. By means of the distributing device 15, the quantity to be discharged is withdrawn from the crystallization tank 2, and the remainder is returned to said tank. The distributing device 15 may consist for instance of a rotatable fork, and the distribution maybe effected by turning the said fork.

Pneumatic conveying devices, in which the medium to be conveyed is made specifically lighter by blowing in air and is thus conveyed, are known per se. However, these devices could heretofore not be successfully used for conveying crystal paste because they have the tendency to get clogged up and are difiicult to control. Therefore, according to the present invention, the conveyor pipe is widened at both ends in a trumpet-like manner, and the pneumatic conveying device is equipped with an automatic scavenging arrangement. The scavenging is effected by an addition of water over a short period into the air feeding lines. Tests have proved that the static pressure in case the air lines clog up may increase by from 50 to 100%. By controlling an automatic valve for instance a magnetic valve so as to bring about a Water scavenging, and by an impulse release by means of an air pressure gauge, an automatic control may be effected.

Referring now to FIG. 2, the arrangement illustrated therein represents a two-stage crystallization apparatus. Mordanting liquid from a mordanting installation is through a pipe line 1 continuously fed into the crystallization tank 2 in which the pro-cooling of the mordanting liquid is effected as in FIG. 1. By means of the pneumatic device 12, mordanting liquid is continuously withdrawn from the crystallization tank 2 and is partially returned thereto and partially conveyed to the next crystallization tank 23. By means of the above described distributing device 15, always that quantity of liquid is drawn into the next following tank which is required for carrying out the respective crystallization operation. In the crystallization tank 23, which as to its construction and inserts corresponds to the crystallization tank 2, the cooling of the mordanting liquid is continued. Through the pneumatic conveying device 12 of the crystallization tank 23, the cooled mordanting liquid is through the dis tributing device 15 conveyed to a centrifuge 25 in which the mordanting liquid is separated from the crystals. The regenerated mordanting solution is then through conduit 27 returned to the mordanting installation.

The separated salt is collected in container 26. The

overflow 24 of the crystallization tank 23 is likewise connected to the centrifuge 25. When the apparatus is at a standstill, the contents of the crystallization tanks 2 and 2.3 may be discharged into the conduit 33 which likewise leads to the mordanting installation.

With the arrangement shown in FIG. 2, also three, four or more crystallization tanks may be arranged in series. By providing a' greater number of crystallization tanks, the cooling effect of counter-current coolers may be obtained without the necessity of providing pumps between the individual containers or arranging the tanks one above the other.

FIG. 3 illustrates an advantageous embodiment of a pneumatic conveying and agitating device combined to a structural unit. Into the conveying pipe 13. and through the nozzle ring 14, air is blown which is metered into the nozzle ring 14 through a conduit system 6, valve 16 and conduit system 28. The conveyor pipe 13 has both ends widened in a trumpet-like manner thereby preventing growing crystals from decreasing the conveying cross sec tion. The conveyor pipe 13 leads into the head container 11. The conveyed liquid is by means of an impact and deviating body 17 directed against the wall of the head container 11 and is along the inclined bottom 13* of head container 11 passed through a pipe and to an adjustable distributing device 15. Container 11 is by means of supports 30 connected to a base plate 3; which simultaneously forms a portion of lid 21 of the crystallization tank 2. Coanially arranged around the conveyor pipe 13 is a further pipe 32 through which air is conveyed to the nozzle ring 5 through a conduit 6 and valve 8. Container 11, conveyor pipe. 13, pipe 3?. and base plate 31 are advantageously combined to a closed unit.

The above outlined embodiment of a pneumatic conveying and agitating device forms a closed unit which is easily exchangeable and which offers little resistance to an agitating movement while having no surfaces or corners where crystalscould collect.

The advantageous behavior of the method according to the invention has been verified with a testing device. With cooling containers of thesame dimensions and the same throughput, the following comparative results were obtained;

Apparatus Apparatus of hereto- According fore Conto Present ventional Invention Structure Crystals not picned up bE the centrifuge pcrcent 15 10 kcal. 500 v Heat transfer value 14 grd. 200

Cleaning of the installation required in view of crystal growth after" hours 8 200 Operators required- Yes N o The method according to the present invention is also suitable for carrying out a number of further crystallization operations in the chemical and metallurgical industries, also in connection with the carrying out of fractional crystallization operations, devices for separating the respective crystal fraction being arranged between the individual crystallization tanks.

It is, of course, to be understood that the present invention is, by no means, limited to the particular method and devices set forth above but also comprises any modifications within the scope of the appended claims.

What I claim is:

1. In a method of continuously crystallizing iron sulfate-heptahydrate from sulfates of mordanting solutions, the steps of: introducing the liquid to be processed into at least two vertically arranged substantially coaxial intercommunicating chambers and continuously circulating the same therethrough in a closed path so that said liquid moves upwardly in one of said chambers and downwardly in the other chamber said circulation of the liquid upwardly being at a velocity less than the settling rate of at least the larger crystals to be formed in the solution, cooling said liquid while it is being circulated through at least one of said chambers to cause crystal formation therein, introducing compressed precooled air into the lower portion of said one chamber to cause upward movement of the liquid therein and to cool said liquid and effecting said introduction in the upward direction in an annular region concentric with said one chamber and spaced upwardly from the bottoms of the chambers so as to leave a quiescent zone in the liquid adjacent the bottoms of the chambers, conveying crystals deposited in the region of the bottom of said chambers together with en trained liquid in an upward direction and along a second path independent of the liquid path, and withdrawing the upwardly conveyed crystals and entrained liquid at a region above said chambers.

2. A method according to claim 1, which includes the step of controlling the supply of compressed air so that the said velocity of liquid movement during circulation upwardly thereof will be greater than the settling rate of fine crystals but less than the settling rate of large crystals.

3. A method according to claim 1, which includes the steps of: moving the said deposited crystals and entrained liquid upwardly along said second path in a quantity in excess of the required rate of crystal output with respect to the rate of liquid input, and at said region above said chambers branching oil a portion of the upwardly moved deposited crystals and entrained liquid for conveying the same to an adjacent container while returning the remainder thereof to said chambers. 4. A method according to claim 2 in which the liquid is cooled in the chamber in which upward flow thereof takes place and in a region located vertically above the region of introduction of said pre-cooled air into the liquid.

5. In a method of continuously crystallizing iron sulfate-heptahydrate from sulfates of mordanting solutions, the steps of: introducing the liquid to be processed into a vertical cylindrical vessel having an annular baflle therein dividing the vessel into co-axial inner and outer chambers interconnected at the top and at the bottom, introducing compressed precooled air into the lower portion of said one chamber to cause upward movement of the liquid therein and to cool said liquid and eflecting said introduction in the upward direction in an annular region concentric with said one chamber and spaced upwardly from the bottoms of the chambers so as to leave a quiescent zone in the liquid adjacent the bottoms of the chambers, whereby the liquid moves in a closed path through said chambers, regulating the supply of the said air so the velocity of the liquid upwardly in said one chamber is less than the settling rate of larger crystals to be formed in the liquid, cooling the liquid in at least said one chamber in a second region thereinextending vertically upwardly above said annular first region whereby the liquid is admixed with the air during its travel through said second region, collecting crystals at the bottom of said chambers, moving the crystals and liquid entrained therein from the bottom of the chambers upwardly along a path independent of the liquid path, and withdrawing the crystals and entrained liquid above said chambers.

References Cited by the Examiner UNITED STATES PATENTS Re. 15,119 6/18 Marsh et al. 23305 1,256,068 2/ 18 Sommer 23305 1,693,786 12/28 Isaachsen 23301 1,997,277 4/35 Burke et a1 23273 2,288,667 7/42 Allen et al. 23273 2,470,822 5/49 Johnson et a1. 23273 2,492,333 12/ 49 Swindin 23273 2,616,790 11/52 Swindin 23273 2,631,926 3/53 Eckstrom 23273 X 2,664,349 12/53 Sable 23301 2,827,366 3/58 Saeman 23273 2,983,589 5/61 Areus 23295 3,071,447 1/ 63 Bernhardi 23273 FOREIGN PATENTS 102,539 9/41 Sweden.

NORMAN YUDKOFF, Primary Examiner.

MAURICE A. BRINDISI, ANTHONY SCIAMANNA,

Examiners. 

1. IN A METHOD OF CONTINUOUSLY CRYSTALLIZING IRON SULFATE-HEPTAHYDRATE FROM SULFATES OF MORDANTING SOLUTIONS, THE STEPS OF: INTRODUCING THE LIQUID TO BE PROCESSED INTO AT LEAST TWO VERTICALLY ARRANGED SUBSTANTIALLY COAXIAL INTERCOMMUNICATING CHAMBERS AND CONTINUOUSLY CIRCULATING THE SAME THERETHROUGH IN A CLOSED PATH SO THAT SAID LIQUID MOVES UPWARDLY IN ONE OF SAID CHAMBERS AND DOWNWARDLY IN THE OTHER CHAMBER SAID CIRCULATION OF THE LIQUID UPWARDLY BEING AT A VELOCITY LESS THAN THE SETTLING RATE OF AT LEAST THE LARGER CRYSTALS TO BE FORMED IN THE SOLUTION, COOLING SAID LIQUID WHILE IT IS BEING CIRCULATED THROUGH AT LEAST ONE OF SAID CHAMBERS TO CAUSE CRYSTAL FORMATION THEREIN, INTRODUCING COMPRESSED PRECOOLED AIR INTO THE LOWER PORTION OF SAID ONE CHAMBER TO CAUSE UPWARD MOVE- 